The invention relates to a hydraulic fluid delivery or circulation device (such as a pump) with a displacement unit mounted in a housing and set in rotation through a drivable shaft unit and which comprises a rotor mounted rotationally secured on the shaft in a pump chamber, and with means which during rotation of the rotor produce at least a first region (suction region) with increasing volume and at least a second region (pressure region) with reducing volume, wherein the first region is connected to a suction connection of the delivery device and the second region is connected to a pressure connection of the delivery device.
Hydraulic delivery devices of the above kind are known. These are formed for example as vane pumps, locked vane pumps, rotary piston pumps or the like. It is known to use delivery devices of this kind in power steering devices, auxiliary braking devices or the like in motor vehicles wherein hydraulic oil is pumped out of a tank to a hydraulic consumer with an attendant increase in pressure.
It is likewise known for the pump chamber to be defined by surfaces which are aligned radially relative to the shaft and abut the rotor in pressure-tight manner, and for the pump to have communicating ducts to the at least first and second regions and to have a flow regulator arrangement for regulating the volume flow of the delivery device.
It is also known to drive the delivery device through an internal combustion engine of the motor vehicle wherein a speed of the rotor of the delivery device is changed in accordance with the rotational speed of the combustion engine of the vehicle. The delivery device then produces a volume flow which fluctuates in dependence on the speed of the internal combustion engine and thus the speed of the delivery device. In order to establish a substantially constant maximum volumetric flow at a consumer, flow regulator arrangements are known which are integrated in the delivery device and by means of which a booster connection from a pressure region to a suction region of the delivery device can be released. A number of guide paths (ducts) are hereby established inside a housing of the delivery device which have to be coupled in sealed manner to the pressure or suction regions of the displacement unit.
It is further known to journal the shaft of the delivery device in bearing regions of the housing. As a result of the pressure-tight guidance of the rotor inside the pump chamber it is necessary to provide a bearing for the shaft with the smallest possible bearing clearance and at the same time to mount the shaft pressure-tight using the fewest possible individual parts.
Furthermore the invention relates to a hydraulic delivery device having a displacement unit mounted in a first part of a housing and comprising a rotor which can be set in rotation through a drivable shaft, and with a cover for closing the first housing part as well as with a holder for the delivery device connected to the cover.
The first housing part can be closed by a cover on which a holder for the delivery device is screwed. As a result of this type of connection the cover which in known delivery devices is made from aluminum and is usually made by the pressure die casting method, is relatively large so that a correspondingly large installation space has to be prepared for the delivery device. This is disadvantageous particularly when using the delivery device in connection with a vehicle since here the delivery device is accommodated for example in the engine compartment in which the space available for the delivery device is only very small.
The invention further relates to a hydraulic delivery device with at least one displacement unit mounted in a housing wherein the displacement unit is connected to a suction connection and to a pressure connection of the delivery device, and the suction connection is connectable to a source, more particularly a tank, supply container, reservoir or the like of a medium to be delivered, through a pipe fitting which can be connected pressure-tight to the suction connection.
Furthermore the invention relates to a method for assembling a delivery device wherein a pipe fitting which engages on a housing of the delivery device and is connected pressure-tight to a suction connection can be positioned for connecting with a pipeline leading to a source of the medium which is to be delivered.
The displacement unit mounted in the housing sucks in the oil through a connecting pipe, by way of example a flexible pressure hose, and delivers this through an increase in pressure to the power steering. A connection between the suction connection of the delivery device and the connecting pipe is produced through a pipe union onto which the connecting pipe can be pushed. It is already known to make the pipe union of plastics. A connection between the pipe union and the housing of the delivery device is made so that the pipe union engages in a blind opening wherein an external circumference of the pipe union corresponds substantially to an inner circumference of the blind opening, and the blind opening has at least one radially inwardly pointing projection which engages in a corresponding recess of the pipe union. Axial fixing of the pipe union is hereby achieved. In addition a sealing device is provided between the housing and pipe union to allow a pressure-tight connection.
Through a snap-fitting or detent connection between the pipe union and the housing of the hydraulic delivery device the pipe union can be turned in the blind opening after the hydraulic delivery device has been fitted, for example in the engine chamber of a motor vehicle. It is hereby possible to align the pipe union in order to find the best possible position for connecting the connecting pipe to a tank which contains a medium which is to be delivered. With the known hydraulic delivery device it is a disadvantage if the pipe union can turn inside the blind hole once fitting has taken place. This can lead for example through the appearance of vibrations during use of the hydraulic delivery device to a distortion of the pipe union so that a connection between the pipe union and connecting pipe to the tank can leak or even come undone in an extreme case.
The invention further relates to a hydraulic delivery device having a displacement unit which delivers a medium from a suction connection standing under the output pressure to a pressure connection connectable with a consumer and standing under the consumer pressure, and a regulating device for adjusting or restricting a volume flow conveyed by the delivery device. In the sense of the invention output pressure is to mean suction intake pressure, input pressure or the like which as a rule is smaller than or equal to atmospheric pressure.
Delivery devices of this kind are normally driven by the internal combustion engine so that with a fluctuating speed of an output shaft of the combustion engine the pump speed is likewise subject to fluctuation. Through the fluctuating pump speed a variable volume flow is set by means of the hydraulic delivery device and likewise rises as the pump speed increases. A consumer connected to the pump requires per se only a certain maximum volume flow so that too much volume flow is set by the pump at high speeds. It is known here to provide the pump with a flow regulating valve which regulates a volume flow to a consumer by releasing an outflow channel from a pressure side to a suction side of the pump.
It is known to equip flow regulating valves of this kind with an additional throttle function. To this end a valve piston of the flow control valve has an axial projection which can be passed through a fixed orifice. The free through-flow cross-sectional area of the orifice is adjusted according to the position of the valve piston. This produces an additional throttling of the volume flow which is dependent on the flow regulating piston. The drawback here is that the throttle function is linked to the function of the flow regulating valve so that this likewise throttles dependent on the path of the flow regulating valve. Furthermore a throttle function of this kind is dependent on the pressure in the pressure collecting chamber of the delivery device (operating pressure) since the flow regulating valve is regulated by a difference in pressure between the pressure in the pressure collecting chamber of the delivery device and the consumer pressure. Furthermore there is the drawback that through the combination of the flow regulating valve with the throttle a relatively expensive assembly is required which has to be carried out with great care in order to be able to set exact volume flow characteristics. The flow regulation and throttling must be matched precisely with each other in order to be able to set a desired volume flow characteristic of the hydraulic delivery device.